In general, production of fructose 1,6-diphosphate (hereinafter referred to as "FDP") is effected by synthesizing FDP from:
(1) glucose and phosphoric acid through the Harden-Young type fermentation of yeast cells, or PA1 (2) glucose and the like in the presence of acetate kinase-containing cells or extracts thereof, and acetyl phosphate (U.S. Pat. No. 5,094,947, hereby incorporated by reference); and then purifying the thus synthesized FDP by:
(A) forming its precipitate using a calcium or barium salt (Arch. of Biochem., vol. 3, pp. 33-44, 1943), PA2 (B) forming its ferric salt (U.S. Pat. No. 4,530,902), or PA2 (C) subjecting it to a column separation method (U.S. Pat. No. 4,575,549).
Since FDP purified in accordance with the above process (A) or (B) contains impurities, such as inorganic phosphate and the like in substantial amounts, it is necessary to carry out additional purification procedures when the product is used as a pharmaceutical preparation. In order to purify FDP to a pharmaceutically acceptable level of purity, it had been formerly proposed to use the aforementioned process (C) in which FDP is isolated making use of ion exchange resin chromatography. This process, however, requires a cation exchange treatment as the first step. Since FDP solution becomes acidic by such a treatment, proteinous materials contained as impurities in the solution are denatured and precipitated, and the thus formed precipitate obstructs the passage of the FDP solution through the cation exchange column. Therefore, it is necessary to remove the proteinous impurities from the FDP solution prior to the cation exchange treatment, by denaturing and precipitating the proteinous impurities through heat or hydrochloric acid treatment. However, during such a pretreatment step, FDP is also denatured and lost to some extent, thus lowering the final FDP yield.